Lengthened Spellcasting (3.5e Variant Rule)
From D&D Wiki
This variant attempts to fix a number of things inherent within the 3.5 system;
- Many casters are often overpowered due to spells that can potentially cripple the enemy without any chance of retaliation on a single failed save, or spells that don't even give a save at all. This variant gives enemies an opportunity to interrupt spellcasting.
- Majestic spells of awesome power with long incantations don't seem to fit taking the fraction of a turn that players get. (Since a whole round is approximately 6 seconds, and a character gets only a small part of that for their round.) This variant allows a character to incorporate words of arcane power, rituals such as lighting a candle, or intense hand gestures into their spells where before one barely had time to say more than two words.
- One usually has to ready a Dispel Magic to counterspell an opponent's spell, which sometimes leads to rounds wasted especially if one doesn't succeed in counterspelling.
To fix these issues, we have the following variant:
The casting times of spells (and other spell-like effects such as psionic powers) are lengthened to one round, casting beginning at the start of the caster's turn and ending at the beginning of their next turn. Spells that normally take a swift action to cast (including Quickened spells) now take a standard action to cast. Immediate action spells may still be cast out of turn, but "use up" the caster's standard action on the following round. The caster may designate their target either when they begin casting (good for touch spells, for example) or when they complete the spell (better in the case of area-affecting spells).
There are two primary exceptions to this rule, spells from the Conjuration (Healing) school, and spells with an Instantaneous duration whose main purpose is damage. (The second is primarily decided by the DM, but a good guideline is a spell that deals damage is one whose dice of damage at the minimum caster level equal or exceed one's caster level. Examples include Scorching Ray, Fireball, Cone of Cold, and the like.)